Effects of Environmental Factors on the Diversity of Grasshopper Communities along Altitude Gradients in Xizang, China

Abstract

To determine the grasshopper species composition, altitudinal distribution patterns, and their main drivers, we conducted a study in Xizang using 33 sample plots ranging from 600 to 4100 m. Grasshoppers were collected from August to October during 2020-2022 using sweep nets. A total of 1159 grasshoppers from six families, 28 genera, and 44 species were identified, with Omocestus cuonaensis and Aserratus eminifrontus as the dominant species, comprising 30.03% and 10.26% of total grasshoppers, respectively. The results showed that species richness and the Margalef richness index of grasshopper communities decreased significantly (p < 0.05) with increasing altitude, peaking at 1100-1600 m and lowest values at 2600-3100 m. Similarly, the Shannon-Wiener index and Simpson dominance index also decreased significantly (p < 0.05) with an increase in altitude, showing the highest and lowest values at 600-1100 m and 3100-3600 m, respectively. The Jaccard similarity coefficients among grasshopper communities varied from 0 to 0.40 across altitudinal gradients, indicating different degrees of dissimilarity. The results of Pearson correlation analyses showed that the Shannon-Wiener index, species richness, Margalef richness index, and Simpson dominance index of grasshopper communities were significantly negatively correlated with the temperature factors and soil pH, but they were significantly positively correlated with the moisture factors. Hierarchical partitioning identified annual mean temperature-daily difference, precipitation in the coldest season, and driest month precipitation as the primary factors explaining variance in grasshopper community diversity in Xizang. These findings provided greater insights into the mechanisms underlying insect community structure, distribution patterns, and diversity in Xizang ecosystems, including implications for the effects of global warming on insect communities.

Keywords: Xizang; altitudinal gradient; distribution pattern; driving factors; grasshopper community structure.

Figure 1

Distribution of sampling points of five vegetation types in the Xizang region.

Figure 2

Sparse curve of grasshopper community at different altitudes in Xizang.

Figure 3

Diversity analysis of grasshopper communities at different altitudinal gradients in the Xizang Region: (A) species richness; (B) individual numbers; (C) Margalef richness index; (D) Shannon–Wiener index; (E) Simpson index; (F) Pielou index. Note: values are mean ± SD of three replicates for each typical vegetation community ecosystem. For each column, values with different letters are significantly different at p = 0.05.

Figure 4

Elevation distribution pattern of grasshopper community diversity in the Xizang region: (A) distribution pattern of species richness; (B) distribution pattern of individual numbers; (C) distribution pattern of Margalef richness index; (D) distribution pattern of Shannon–Wiener index; (E) distribution pattern of Simpson index; (F) distribution pattern of Pielou index.

Figure 5

Heat map of the clustering of grasshopper family-level community structure at different altitudinal gradients in the Xizang region.

Figure 6

Heat map of the Pearson correlation between grasshopper community diversity and environmental factors at different altitudinal gradients in the Xizang region. Note: (A) Correlates with temperature factor; (B) Correlates with moisture factor; (C) Correlates with vegetation and soil factors. The color of the circle indicates the direction of the correlation, where blue indicates positive correlation and red indicates negative correlation, and the darker the color indicates stronger correlation.

Figure 6

Heat map of the Pearson correlation between grasshopper community diversity and environmental factors at different altitudinal gradients in the Xizang region. Note: (A) Correlates with temperature factor; (B) Correlates with moisture factor; (C) Correlates with vegetation and soil factors. The color of the circle indicates the direction of the correlation, where blue indicates positive correlation and red indicates negative correlation, and the darker the color indicates stronger correlation.

Figure 7

Redundancy analysis (RDA) ranking of grasshopper community diversity indices with environmental factors in the Xizang region.

Figure 8

Independent explanatory rates of environmental factors for the grasshopper community diversity in the Xizang region: (A) Independent explanatory rate for a single environmental factor; (B) Explanatory rates for six categories of environmental factors.